#include<bits/stdc++.h>
#define ll long long
#define ull unsigned long long
using namespace std;

const int N = 1e6 + 10, INF = 0x3f3f3f3f;

int n, k, x;
vector<string> s;
vector<string> path, a;

void dfs(int p, string str)
{
    if (p == k + 1) {
        a.push_back(str);
        return;
    }
    for (int i = 1;i <= n;i++) dfs(p + 1, str + s[i - 1]);
}

void solve()
{
    cin >> n >> k >> x;
    for (int i = 0;i < n;i++) {
        string c; cin >> c;
        s.push_back(c);
    }
    sort(s.begin(), s.end());
    dfs(1, "");
    sort(a.begin(), a.end());
    cout << a[x - 1];
}

signed main()
{
    //ios::sync_with_stdio(0);
    //cin.tie(0);cout.tie(0);
#define ONLINE_JUDGE
#ifndef ONLINE_JUDGE
    std::istringstream in(R"()");
    std::cin.rdbuf(in.rdbuf());
#endif
    int T = 1;
    //cin>>T;
    for (int i = 1;i <= T;i++) {
        solve();
    }
}